Gage for low pressures



UNITED A'llhlhl'l" @FMQE.

ELECTRIC AND MANUFACTURING COMPANY, A

COEPGRATION G35 PENNSYLVANIA.

GAGE Fen LOW rsnssuans.

Application filed December 27, 1917.

To all 10/ 2/0117, it may concern: 7

Be it known that I, James E. SHRADER, a citizen of the United States, and a resident of Edgewood, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Gages for Low Pressures, of which the following is a specification.

My invention relates to new and useful improvements in gages for measuring low pressures of gases and vapors and more particularly to animproved form of gage of the radiometer type and somewhat similar to the well-known Knudsen One of the primary objects ofmy invention consists in constructing a. gage of this character which operates by diilerential molecular bombardment of a movable metallic strip caused by heating a fixed metal strip disposed adjacent and parallel to the 7 normal position of the movable film.

A still further object of my invention resides in providing a gage possessing extreme sensitiveness at low pressures which shall, at

the same time, be simple and rugged in construction and easy of operation.

Another object which I have in view is the construction of a gage which, at low pressures, will operate independently of the nature of the gases or vapors being measured.

lVith these and other objects in view, my invention will be more fully described, illustrated in the drawings, and then particularly pointed out in the claims.

In the drawings, Figure 1 is a side eleva tion of my improved gage Fig. 2 is a front elevation; and Fig; 3 is a fragmentary side elevation showing a slight modification in construction.

In the several views of the drawing and throughout the description, like parts'are indicated by corresponding reference numerals.

My improved gage includes a body 10, preferably substantially cylindrical in shape and formed of glass, having a sealed-in sup-' porting stand 11 at its lower end and a drawn-out sealed upper end 12. A tube 13 leads from the chamber, inclosed by this body and is adapted for connection with the vessel containing the gas or vapor, the pres sure of which is to be measured.

Lead-in wires or conductors 14 and 15 are sealed into the stand 11 and their inner ends are bent to provide over-lapping supporting Specification of'Lctters Patent. lfguigntgd July 13 192() Serial No 203,195.

terminals 16 disposed one behind the other. The stand is provided with a laterally oliset extension or tube 17 in the upper end of which is sealed one end of a supporting rod or wire 18, the'opposite end of which isbent downwardly and laterally to provide a supporting terminal 19 disposed vertically above the terminal 16 of one of the lead-in wires. A thin fixed strip or filament 20 of suitable metal has its intermediate portion passed over the supporting arm 19 and its terminals secured to the overlapping ends of the lead-in wires 14 and 15 in the manner best shown in Fig. 2, so that it is held under tension and one stretch of the filament is disposed vertically and axially within the chamber. Obviously, a current passed between the lead-in wires through the strip or filament will heat it in proportion to the resistance which it otters to the circuit.

F or the sake of extreme delicacy, supporting wires or rods 21 and 22 may be substi tuted for the lead-in wires 14- and 15 as the supports for the filament, and relatively light lead-in wires 23 may be sealed into the bottom of the body 10 and connected to the filament immediately beyond the joints of the filament with the supporting wires 21 and 22 so that the relatively large joints necessary for suflicient strength to support the filament will not form part of the circuit, and their resistance will not enter into the problem. Such an arrangement is shown in Fig. 3 and either construction may be employed as deemed advisable.

Sealed into the top of the body 10 is a supporting rod or wire 24 which extends axially of the body and which, at its lower end, is doubly oft-set to provide a supporting arm 25 disposed in parallel and horizontal spaced relation to the supporting arm 19 and in juxtaposition thereto. Secured at one end to the supporting arm 25, so as to normally hang by gravity in parallel close relation to the vertical stretch of the filament 20, is a movable metallic filament or strip 26. This strip may be formed from gold leai or may consist of a line quartz fiber metallically coated with some suitable metal, such as platinum.

In operation, the tube 18 is connected to the vessel containing the gas or vapor, the pressure of which is to be measured, and a measured electric current is sent through the lead-in wires and heating strip orfilament 20. A suitable instrument (not shown) is sistances,and K is a constant for the gage.

connected in this circuit so that the changes in resistance offered by the filament 20, which constitute a measure oi the temperature of such filament, may be determined,

and the deflection oithe movable strip 26 is carefullynoted. Of course, the deflection of this movablestrip is caused by its molecular bombardment by the molecules ofthe gas or vapor being measured, under the influence of the heat of the'vertical strip or the filament 20. The amount of deflection of the This constant K maybe derived from suitable calculations, as will be readily appreciated by any one skilled in the art or by direct comparison of the gage with a standard .or previously calibratedgage, such as a gage oi": the Knudsen type. This com aarison of the gage. should, ho vever, be with a gas or vapor at a pressure earthe upper range of my improved gage, that is, near the lower range of the Knudsen gage as, above such a pressure, accuracy would not be obtained.

The range of operation of a number of gages constructed in. accordancewith my invention, Within which the calibration linear is from 10' to 10- mm. Above the latter pressure, special calibration is required.

To neutralize static charges, the rod or Wire 24k may be connected externally to one of the lead-in wires 14% and 15 and, of course, in use, the body of the instrument, save for a sight opening, Will be Wrapped in foil. 7

It will, of course, be clear that numerous changes in construction and arrangement of parts, particularly in the supports for the fixed, film or filament and for the moving film or strip, may be made and 1,,theretore, reserve the right to make any changes in construction Which shall fall within the scope of the claims.

I claim as my invention:

1.. A gage for measuring low, pressures of. gases or vapors including a vessel providing a chamber, a conductor element fixed Within the vessel, means for. passing current through the conductor element to heat itan'd an element freely supported "for swinging movement and normally in parallel spaced relation to the conductor element.

nlar bombardment of the vane.

2, A gage for low pressures including a vessel providing a chamber, a metallic strip supported in fixed position Within the vessel, means for passing a current through the strip and a metallic strip supported at one rent through the strip, and a movable strip or vane suspended from one end within the chamber and normally in close parallelrelation to the conductor strip. 7 I I '4. A gage for lOW pressuresincluding a vessel providing a chamber, a tube communieating With the vessel and adapted'forconnection with a chamber containing. the gas or vapor, the pressure of which is to be measured, a supporting 'rod extending into the chamber, lead-in iresextending into the chamber,l.a metallic strip or ribbon having its ends connected to the lead-in Wires and its intermediate portion supported under tension by the supporting rod with one stretch of the strip vertically disposed, a second supporting rod extending into the chamber and second. strip or vane secured at one, end to the second supportlng rodand depending for tree swinging movement, the second strip being normally adjacent and parallel to the vertical stretch of the first strip. V v

. 5. A gage for low pressuresincluding a hermetically sealed vessel having a branch tube adapted :lor connection to' a vessel. containing the gas or vapor, the pressure of which is to be measured, a conductor element supported in fixed position Within the vessel, means for passing a current through such element and a vane suspended in 'parallel spaced relation to the conductor element.

6. A gage for low pressures including a hermetically sealed vessel having a branch tube adapted for connection to a vessel containing the gas or vapor, the pressure of Which is to be measured, a conductor ele-' ment supported in fixed position Within the vessel, means forpassing a current through such element and a vane suspended in parallel spaced relation to the conductor eiement, the vane being formed of gold leaf.

7. A gage for low pressures including a vessel providing a chamber, a movablestrip or vane suspended Withinthe chamber and electrically heated means for causing molec- In testimony whereof l have hereunto subscribed myname this 26th day of Dec,

JAMES E. snnannn. 

